Poor Idling

High Idle Speed

Check Engine Control Module (ECM) power source and backup power source circuit. See ENGINE CONTROL MODULE POWER SOURCE CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article and DTC P0560: SYSTEM VOLTAGE under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On Corolla (A/T ) and Matrix (A/T ), check park/neutral position switch. See PARK/NEUTRAL POSITION SWITCH under ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
Check A/C signal. A/C signal may also be referred to as A/C switch signal or compressor circuit. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
On MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
On Corolla and Matrix, check ISC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - COROLLA & MATRIX article.
On MR2 (with standard M/T), check IAC valve circuit. See DTC P0505 & P0511: IDLE AIR CONTROL MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - MR2 article.
On RAV4, check IAC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - RAV4 article.

Low Idle Speed

On Camry (except Solara), Corolla, Matrix, MR2 and RAV4 models, check injector circuit. See DTC P0300: RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
Check Engine Control Module (ECM) power source and backup power source circuit. See ENGINE CONTROL MODULE POWER SOURCE CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article and DTC P0560: SYSTEM VOLTAGE under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
Check A/C signal. A/C signal may also be referred to as A/C switch signal or compressor circuit. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
On all models, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article or on some models, see DTC P0230: FUEL PUMP PRIMARY CIRCUIT under DIAGNIOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
On Corolla and Matrix, check ISC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - COROLLA & MATRIX article.
On MR2 (with standard M/T), check IAC valve circuit. See DTC P0505 & P0511: IDLE AIR CONTROL MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - MR2 article.
On RAV4, check IAC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - RAV4 article.

Rough Idle

On Camry (except Solara) and MR2 models, check ignition coils with ignitor assemblies. See DTC P0351: IGNITION COIL PRIMARY/SECONDARY CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On Corolla, Matrix and RAV4 models, check ignition coils with ignitor assemblies. See DTC P1300: IGNITOR CIRCUIT MALFUNCTION under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On Camry (except Solara), Corolla, Matrix, MR2 and RAV4 models, check injector circuit. See DTC P0300: RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On all models, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article. On some models, see DTC P0230: FUEL PUMP PRIMARY CIRCUIT under DIAGNIOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On vehicles with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
On Corolla and Matrix, check ISC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - COROLLA & MATRIX article.
On MR2 (with standard M/T), check IAC valve circuit. See DTC P0505 & P0511: IDLE AIR CONTROL MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - MR2 article.
On RAV4, check IAC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - RAV4 article.
On all models, check engine compression and spark plugs. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
On Camry (except Solara) models, check MAF meter assembly. See DTC P0100: MASS OR VOLUME AIR FLOW CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.

Hunting & Surging

On Camry (except Solara), Corolla, MR2 and RAV4 models, check spark plugs. Replace as necessary.
Check Engine Control Module (ECM) power source and backup power source circuit. See ENGINE CONTROL MODULE POWER SOURCE CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article and DTC P0560: SYSTEM VOLTAGE under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On all models, check fuel pump control circuit. See FUEL PUMP CONTROL CIRCUIT under COMPUTERIZED ENGINE CONTROLS in appropriate SYSTEM & COMPONENT TESTING article or on some models, see DTC P0230: FUEL PUMP PRIMARY CIRCUIT under DIAGNIOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
On MR2 with sequential manual transaxle, check throttle body and components for Electronic Throttle Control System (ETCS). See THROTTLE BODY under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. Models with sequential manual transaxle may be identified by the shift lever pattern which consists of "R", "N", "S" and "+" in place of the conventional type shift lever pattern and no clutch pedal is used.
On Corolla and Matrix, check ISC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - COROLLA & MATRIX article.
On MR2 (with standard M/T), check IAC valve circuit. See DTC P0505 & P0511: IDLE AIR CONTROL MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - MR2 article.
On RAV4, check IAC valve circuit. See DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION under DIAGNOSTIC TESTS in SELF DIAGNOSTICS - RAV4 article.